He condemned North Korea as a country "ruled as a cult."

"At the center of this military cult is a deranged belief in the leader's destiny to rule as parent-protector over a conquered Korean peninsula and an enslaved Korean people," he added.

He also declared Wednesday that "now is the time for strength" on nuclear-armed North Korea, calling for all countries to join forces against the regime.

"All responsible nations must join forces to isolate the brutal regime of North Korea," he said. 

He also offered North Korean leader Kim Jong-un what he called "a path towards a much better future" as tensions soar over Pyongyang's nuclear ambitions.

"The weapons you are acquiring are not making you safer," Trump said at the South's parliament, in what he described as a direct message for Kim. "They are putting your regime in great danger." "Yet despite every crime you have committed against god and man," he went on, "we will offer a path towards a much better future."  

The US president also took issue with North Korea's abuses of human rights of its people.

The regime has for decades been criticised for a range of rights abuses including torture, rape and execution of perceived critics or those trying to flee the country.  

It is also known to operate multiple prison camps across the country where hundreds of thousands languish under forced labour and starvation. 

Trump noted many cases of such abuses, including "a nine-year-old boy...imprisoned for ten years because his grandfather was accused of treason."

"The horror of life in North Korea is so complete, that citizens pay bribes to government officials to have themselves exported abroad as slaves," he said.

Drawing a sharp contrast between the two Koreas, he used much of the speech to hail the achievement of South Korea. The speech was made one day after he held a summit with President Moon Jae-in.

 After spending three days in Japan, Trump arrived here Tuesday for a two-day state visit. He is on his first Asia trip, which also includes visits to China, Vietnam and the Philippines. 

The Republican president was accompanied by top aides, such as Secretary of State Rex Tillerson, National Security Advisor H. R.

McMaster, Chief of Staff John Kelly and senior advisor and son-in-law Jared Kushner.

Some 550 people attended the speech, including South Korean lawmakers, foreign diplomats and those invited by the Washington government. (Yonhap/AFP)